Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.
Volume 4
Issue 2
Available Online: http://www.ejpau.media.pl/volume4/issue2/horticulture/art-03.html


Eugeniusz Ko這ta, Zbigniew 奸您ak



The studies conducted in a glasshouse of the Establishment of Horticultural Production (PPO) at Siechnice were aimed to determine the reaction of tomatoes grown on mineral wool to CO2 enrichment of the atmosphere and to calculate the profitability of applying this treatment in wholesale production. The studies used liquid gas accumulated in pressure containers. After being evaporated, the gas was carried in liquid form to plants by means of a system of PE pipes. The studies adopted three levels of CO2 content in the glasshouse atmosphere, namely 0.06-0.08% with ventilators closed, 0.04-0.05% with ventilators slightly opened, and 0.03-0.04% with ventilators fully opened.

Key words: tomato, glasshouse cultivation, CO2 enrichment, yield, profitability of cultivation.


In natural conditions for the majority of plants it is not CO2 concentration in the atmosphere that constitutes a factor limiting the intensity of photosynthesis. This fact is taken advantage of in glasshouse cultivation, where plants are supplied with carbon dioxide. Within a certain range, doubling CO2 content in the air also doubles the intensity of photosynthesis, which is of significant importance for the production of biomass [13].

The first Polish experiments on supplying tomatoes with CO2 conducted by Skierkowski [9] showed that a 0.1-0.15% increase of its concentration in a glasshouse secured an increased yield of fruit by 30% and of the early yield by 80%. A similar range of CO2 concentrations in the cultivation of this plant is also recommended by Libik et al. [7], Sowi雟ki [11]. Libik and Repelewicz [6]. According to Mortensen [8], the optimum CO2 concentration for the majority of plants is slightly lower and is placed within the range between 0.06-0.09%. On the other hand, Cydendambajew [2] points out that the optimum CO2 concentration is related to the stage of tomato growth and is equal to 0.06-0.08% in the phase of seedlings production, and 0.1-0.15%, when the plants are fully developed. CO2 enrichment of plants can also be profitable in summer with open ventilators, the aim of which is to keep its concentration at the level up to 400 ppm [10]. This refe rs especially to no soil cultivation, where in the afternoon the level of CO2 can decrease below 100 ppm, which is the value below the compensation point.

Apart from an increase of the fruit yield, especially the early yield, another effect of CO2 supply is an increase of sugar content in the fruit and a considerable drop of acids concentration and resulting from it improvement of organoleptic valours [6]. At the same time attention is drawn to the fact that profitability of this treatment is conditioned by other factors, including the light, air humidity, fertilization and temperature, which should be by 2-3蚓 higher that in cultivation of plants that are not enriched [3, 6].

Despite encouraging results of studies on CO2 enrichment this treatment did not arouse much interest in horticultural practice. It began to be used only in the 1980s in West European countries, and lately also in Poland, especially in cultivation on inorganic subsoils. A possibility of using CO2 free from impurities in the compressed form in cylinders, improvement in the equipment for dosing and controlling the concentration as well as greater air-tightness of glasshouse construction contribute to the popularity of enriching plants with CO2.

The purpose of the studies was to determine the effect of CO2 application on the production and economic effects of glasshouse wholesale production of tomatoes.


The studies were conducted at the Establishment of Horticultural Production Siechnice near Wroc豉w, in the conditions of wholesale production of glasshouse tomatoes, where in 1991 this vegetable started to be cultivated on mineral wool with computer control of the climate, fertilization and irrigation. Beginning with 1997, plants were enriched with carbon dioxide, which was supplied to the glasshouse atmosphere.

PPO Siechnice uses a prolonged method of tomato cultivation, where seed sowing is performed on December 10-15, while the seedlings cultivated in blocks are planted from mats to mineral wool 40 days after the sowing date and plant density is 2.4 plants per 1 m2. Plants are led in one stem and the topping takes place at the beginning of September. Large scale introduction of biological methods of protecting plants from greenhouse while fly and red spiders made it possible to use bumble-bees for plant pollination. The fruit are picked 3 times a week. The final harvest was joined with closing down the plantation is in the middle of December.

Plant enrichment is conducted throughout the period of tomato cultivation on a permanent place, with the use of liquid CO2. The whole system of enriching the greenhouse atmosphere in this gas is comprised of the following:

Three levels of CO2 content were adopted in the greenhouse atmosphere in the production of tomato:

CO2 dosing was used in the spring period between 9.00 am.-3.00 pm, and in the summer and autumn periods between 7.00 am-5.00 pm.

The total area of tomato cultivation under the studies was 4 ha every year. The results obtained in 1994-1996 helped to estimate the yielding of plants that were not enriched, while the results from 1998-2000 were achieved with CO2 enrichment. The year 1997 was not considered in the studies because the cultivation was damaged by flood.

The mean weekly yield of fruit from the whole period of tomato yielding was used to evaluate the commercial yield. An analysis of price tendencies on the greenhouse vegetables market was the basis to distinguish the very early and early yields. On the basis of the data from all the examined years, the very early yield, calculated since the first permanent reduction of prices for fruit, was considered to mean all the crops gathered in the period up to the 19th week of the calendar year. On the other hand, the early yield was considered to mean the crop gathered since the above time until the next reduction of prices in the third ten days period of June (a period of 19th-25th weeks of the year).

In the economic estimation on the basis of weekly crops of fruit signifying the means for the years with and without CO2 enrichment and the market prices of the year 2000 the gross income from tomato cultivation was calculated. Besides, the costs of enrichment were worked out and they consisted of the price of CO2 purchase, the cost of leasing the tanks and evaporating dished, amortization, expenditure of electrical energy, the costs of services, repairs and maintenance. These data were used to calculate the economic indexes, namely the index of profitability and the relative costs of CO2 enrichment in relation to additional incomes achieved after the treatment was introduced.

From among the weather data the paper chose to present only the measurements of insolation as a factor that is not controlled in greenhouse cultivation (table 1). Calculating the mean monthly insolation in the years 1994-1996, when the plants were not enriched, and in the years when they were (1998-2000), it can be stated that it was slightly higher for the tomatoes that were not enriched. This means that when the other elements of greenhouse micro-climate was kept on the same level year by year, an increased yield of fruit in the years with CO2 enrichment was solely the effect of this treatment.

Table 1. Mean monthly insolation during the cultivation of greenhouse cultivation at PPO Siechnice in the years 1994-2000


Years 1994-1996
without enrichment

Years 1998-2000
with CO2 enrichment

Mean number of sunny hours
in a month



Deviation from the mean monthly insolation for the years 1992-2000 in the times



Deviation from the mean monthly insolation for the years 1992-2000 in %




In all the analyzed years the fruit harvest began in the 13th week of the calendar year, i.e. on the first days of April. The year 1999 was an exception because then the beginning of the harvest was a week earlier. In all the examined years very intensive ripening of the fruit and consequently increased crops were observed beginning with the 16th week of the year (third 10-day period of April). The yielding was decreased after 38th-39th week in the variant without CO2 enrichment, and after 44th-45th week in the variant with CO2. The harvest was finished after the 48th week that is in the first half of December, independent of the use of CO2 application.

The results concerning tomato yielding showed slight differentiation in the successive vegetation seasons. That is why they are presented as mean figures for the period of 3 years. It follows from the data in figure 1 that supplying plants with carbon dioxide gave a significantly higher yield, mainly at the beginning of the harvest, between the 13th and 19th weeks of the calendar year. In the successive period the effect of CO2 enrichment was differentiated; the plants supplied with CO2 showed both increases and decreases of the yield in relation to the cultivation without CO2 enrichment. In the autumn period, however, the studies again observed high effectiveness of this treatment in the 39th-46th weeks.

Figure 1. Differences in the commercial yield of greenhouse tomato enriched with CO2 in relation to the cultivation without this treatment, weekly in kg from 1 ha

In sum, percentage increase of the yield calculated from the beginning of the harvest in the successive weeks of the year (figure 2) showed very high efficiency of this treatment during the first 3 weeks of yielding, when it reached 250% in relation to the cultivation without CO2 enrichment. In the successive 4 weeks the yield was lowered to 30% showing further slow decrease in the summer period and increase in autumn.

Figure 2. Total increase of the commercial yield of greenhouse tomato achieved under the effect of CO2 enrichment, calculated from the beginning of the crops in successive weeks of the year (in %)

The data contained in table 2 and referring to the whole period of cultivation show that in conversion per 1 m2, supplying plants with CO2 caused an increase of the commercial yield of fruit from 38.1 to 45.5 kg, of the early yield from 8.8 to 9.7 kg, and of the very early yield from 5.0 to 7.5 kg. A high, up to 50% increase of the very early yield points at especially high effectiveness of the treatment at the beginning of the cultivation and fruit harvest of tomato. That increase was also significant in reference to the overall commercial yield and it was 19.4%.

Table 2. Effect of plant enrichment with CO2 on the yielding on greenhouse tomato (kg/m2)

Successive weeks

Type of yield

Cutlivation without CO2 enrichment

Cultivation with CO2 enrichment

Increase of yield
under the effect
of CO2 enrichment (in %)


very early










the remaining part of the yield





total commercial yield




It can be stated on the basis of the data from table 3 calculated from the data of the year 2000 that the purchase of CO2, including the costs of leasing evaporating dishes and tanks, constituted the highest proportion in the costs of plant enrichment. The following important item in the costs was servicing the enriching devices. Its proportion in the total costs was 35.5%. The financial outlays including amortization, repairs and maintenance of the dosing and controlling devices constituted a relatively small percent. The total cost of enrichment per 1 ha of tomato cultivation was determined to be 51 037.20 PLZ, which with simultaneous increase of the gross income by 306 123.50 PLZ (22.3%) ensured the clear income of 255 086.30 PLZ from 1 ha in consequence of applying CO2 enrichment (table 4). High profitability of enriching greenhouse tomatoes with carbon dioxide is proved by the index of relative co sts, which is 16.67% and the index of profitability, which reaches 499.80%.

Table 3. Costs of CO2 enrichment in the cultivation of greenhouse tomato according to the data from 2000

Amount of the used CO2 and specification of costs


Amount of used CO2 (in kg/ha)

66 343.00

Price of CO2 purchase (in PLZ/ha)


Costs of leasing tanks and evaporating dishes (in PLZ/kg CO2)


Costs of used CO2 (in PLZ/ha)

26 537.20

Costs of servicing the enriching devices (in PLZ/ha)

18 000.00

Costs of electrical energy (in PLZ/ha)


Repairs and maintenance (in PLZ/ha)

3 000.00

Amortization of enriching devices (in PLZ/ha)

3 000.00

Total cost of CO2 enrichment in the cultivation of 1Ha tomato (in PLZ)

51 037.20

Table 4. Basic economic indexes in the cultivation of greenhouse tomato with CO2 enrichment



Gross income (in PLZ/ha)


with CO2 enrichment

1 679 826.74

without CO2 enrichment

1 373 703.24

Increase of gross income under the effect of CO2 enrichment (in PLZ/ha)

306 123.50

Clear income achieved under the effect of CO2 enrichment (in PLZ/ha)

255 086.30

Proportion of CO2 enrichment costs in the additional gross income (in %)


Profitability index of enriching plants with CO2 (in %)



The new technology of production, using the mineral wool as the subsoil, the system of plant fertigation and steering the greenhouse climate of PPO Siechnice made it possible to achieve an increase of the yield of tomato fruit in the prolonged cultivation up to 38.1 kg/m2, which made the cultivation profitable. Applying CO2 in plant enrichment, which began in 1995 and is now used in all greenhouse cultivation, was considered to be a condition of further improvement of the productive and economic effectiveness.

The studies conducted in the years 1994-2000 showed that the increase of tomato yield achieved under the effect of supplying plants with carbon dioxide in the conditions of wholesale production was lower in relation to the increase obtained on an experimental scale by Skierkowski [9], Hartz, et al. [4], Libik and Repelewicz [6] and quoted by Sowi雟ki [11].

This can be accounted for both by greater difficulties in achieving the optimum conditions in a huge wholesale object and by the applied CO2 concentration, which was kept at the level of 0.06-0.08% with closed ventilators, and only 0.03-0.04% with open ventilators, doing away with the deficit of the gas intensively utilized in the process of photosynthesis.

An increase of the commercial yield of fruit from 38.1 to 45.5 kg/m2 should be considered to be fully satisfying, especially when one considers the fact that the highest increase was observed at the beginning of fructification. It turned out that the increase of the very early yield achieved during the first 7 weeks of yielding (until the middle of May) reached 50%, which considering very high retail prices had a significant influence on the application of this treatment. When Libik and Repelewicz [5] applied CO2 enrichment in the concentration 800 ppm, they found out an increase of the yield of early fruit within the range of 77-98% depending on the year, which has a decisive effect on the financial outcome if one takes into account a 27% increase of the total commercial yield and more favourable price relations at the beginning of the crop. High efficiency of the treatment of CO2 enrichment at that time can be accounted for by the fact that young plant s show a more positive reaction towards the content of this gas in the atmosphere, because in older plants a genetically conditioned drop of photosynthesis intensity takes place [1, 12].

At PPO Siechnice enrichment with CO2 contributed to higher gross income by 22.3%, which with relatively low costs of the application of the treatment gave a very high profitability rate of 499.8%. Hartz et al. [4] also point at high profitability of CO2 enrichment. They establish its costs at 10% of the total costs of tomato production. On the other hand, Skierkowski [9] found out a 20% increase of the value of the fruit yield in the spring cultivation and no effectiveness of the treatment in the autumn cultivation. It should be emphasized, however, that these results were obtained on traditional subsoil, where no radical drop of the level of CO2 caused by intensive photosynthesis process in the greenhouse atmosphere takes place.


Results of the studies conducted in the years 1994-2000 and concerning profitability of enriching greenhouse tomatoes with carbon dioxide point at the following conclusions:

  1. CO2 enrichment on a permanent place on the subsoil of mineral wool gave increased commercial yield of fruit from 38.1 to 45.5 kg/m2 (by 19.4%)

  2. A positive effect of enriching the atmosphere with CO2 was especially revealed in the case of the very early yield of fruit, which had a decisive importance for the economic profitability. That yield gathered from the beginning of April till the middle of May was for the period of 3 years higher by 50% in relation to the cultivation without enrichment.

  3. The influence of CO2 enrichment on the economic effect of tomato cultivation was shown in increased clear income by 22.3%

  4. The rate of relative value of additional costs of CO2 enrichment was 16.67%, while the rate of profitablity reached the value of 499.8%.


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  10. Slack G., Hand D.W., 1985. The efect of winter and summer CO2 enrichment on the growth and fruit yield of glasshouse cucumber. J. Hort. Sci. 60(4), 507-516.

  11. Sowi雟ki P., 1994. Carbon Dioxide: Natural Fertilizer in Greenhouse Production. Bromatologia, Warszawa, 1-6 [in Polish].

  12. Starzecki W., Mydlarz J., 1982. Increase in photosynthetic rate in tomato leaves included by compensation low intensity radiation by increased CO2 concentration. Acta Physiologiae Plantarum 1(3), 215-221.

  13. Strza趾a K., 1998. Physiological and Ecological Aspects of Photosynthesis. Collective Work Bases of Plant Physiology. PWN, Warszawa, 263-269 [in Polish].

Eugeniusz Ko這ta
Faculty of Horticulture
University of Agriculture in Wroc豉w
7 Rozbrat Street, 50-334 Wroc豉w, Poland
tel. (+48 81) 533 82 41
e-mail: kolota@ozi.ar.wroc.pl

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